A user, who receives provision of service from a server on a computer network, may use the service provided by each of a plurality of servers. In this case, if the user receives individual authentication in each of the servers individually every time the user receives the provision of service, the burden of the user is increased. In this case, each of the servers individually manages account information of all the users to which the server provides the service, management load of a manager of the server is increased.
There is a technique called Single Sign-On. Single Sign-On is an authentication technique for using resources on a plurality of computers by a single action of authentication processing. In general, according to Single Sign-On, in a server having a prescribed relationship with another server in which a user is authenticated, the service is provided to the user without the user authentication in the server. For example, there is a technique for enabling Single Sign-On for accessing a plurality of networks existing in a plurality of domains. For example, Japanese National Publication of International Patent Application No. 2008-506139 is disclosed as the related art.